1. Field of the Invention
The present invention relates to the cutting of circular slots in paved "traffic surfaces" that extend about manhole castings and the like to permit castings and surrounding cores of pavement to be removed quickly and easily for such purposes as elevating the level of manhole castings to align with new pavement. More particularly, the present invention relates to the use of a novel and improved core-cutting apparatus to cut circular slots in traffic surfaces wherein the apparatus has a transport carriage to which are connected operating components that typically include a large diameter, generally cylindrical core-cutting bit, power-operated support and drive systems that mount the bit for vertical and rotary movement relative to the carriage along and about a vertically extending center axis, and a power-operated stabilization system that makes use of the weight of the apparatus in maintaining desired positioning of the apparatus during cutting operations.
2. Prior Art
The term "traffic surface" is used in this document in a generic sense to refer to a wide class of substantially horizontally extending paved surfaces such as highways, streets, driveways, parking lots, runways, taxi-ways, tarmacs, floors of large garages and industrial buildings, loading dock decks, and the like that have metal castings or other structures installed therein to define manholes, catch basins, access openings for valves, fluid supply connections or water or fuel, electrical supply connectors and the like.
Because traffic surfaces are exposed to wear and often to the effects of the elements, they are subject to deterioration and periodically require repair and/or resurfacing, typically by installing one or more additional layers of paving material such as asphalt atop portions of existing pavement. When pavement is to be replaced or pavement layers are to be added, it is customary to remove installed metal castings by utilizing impact tools such as jackhammers to break existing pavement from about the castings so that the castings can be removed and reinstalled, often accompanied by "riser" castings designed to aid in accommodating the level of new pavement.
The use of jackhammers to effect pavement removal from about installed manhole castings and the like is both "time intensive" and "labor intensive" in that it typically requires an hour or more of relatively strenuous work by at least two people. Operating a jackhammer is physically taxing in that it quickly tires workers, risks the onset of back problems and other possible injuries, creates a high level of noise, often releases undesirably large quantities of dust into the air, and tends to cause chips and small pieces of hard material to be discharged about the job site so as to pose a hazard not only to workmen but also to passers by.
Using a jackhammer to break apart pavement to facilitate its removal also tends to have a number of deleterious effects on surrounding pavement that is left in place. Pavement left in place typically has rough, structurally weakened edge regions wherein hairline cracks are formed that can lead to leaching and to the formation of cracks of far greater size. Reinforcing rods located in pavement that remains in place often have been undesirably loosened by jackhammer usage. Moreover, as the use of a jackhammer almost invariably leads to some greater pavement breakage than is desired, more pavement than is necessary tends to be removed, which not only adds significantly to the cost of pavement replacement but also causes larger than necessary piles of broken pavement to accumulate--accumulations that need to be removed before proper traffic flow can safely be restored. Clearly a pavement removal technique that is more in line with preserving the structural integrity of roadway infrastructure is desired.
In recognition of such drawbacks as are mentioned above, a variety of forms of apparatus have been proposed that are intended to be capable of cutting circular slots in pavement to permit removal of manhole castings and the like together with cores of surrounding pavement material. However, such proposals typically have exhibited one or more drawbacks--drawbacks that have been deemed to be sufficiently serious in nature to prevent widespread acceptance.
For example, in an effort to provide core-cutting apparatus that easily can be moved from one job site to another, an approach taken by some proposals has been to provide a relatively lightweight unit that includes a relatively large diameter core-cutting bit and a supporting frame of relatively small size that is configured to permit the unit to be mounted as an "attachment" on various forms of construction equipment such as trucks, tractors and road graders. Prevalent among drawbacks that tend to be exhibited by such proposals is the tendency of the provided apparatus to be so light in weight and lacking in rigidity that the generation of a proper type of cutting action tends to be inhibited by chatter and vibration of the bit, and by failure to provide sufficient stabilization to ensure that proper positioning of the bit is maintained during the time that is required to cut circular slots of proper depth.
The presence of vibration, and the lack of needed support and stabilization for a core-cutting bit can result in undesired "walking" of the bit and in undesired movement of the apparatus. The effect of unwanted movement of the apparatus during operation of the bit not only tends to cause improper types of core cutting to result, but also tends to cause undue wear on the bit, tooth breakage, bit failure and/or undue wear on components of the apparatus that mount and operate the bit.
Not provided by prior proposals is an apparatus that can be transported expeditiously between job sites, that can be quickly and effortlessly positioned and repositioned at a job site to perform core cutting operations about a series of spaced manholes, that will, with reliable stability, maintain desired operating positions without "walking" or otherwise moving about while cutting is underway, and that will repeatedly perform properly (without encountering frequent tooth breakage or other bit damage) to efficiently precision-core one manhole after another.